Bolometer construction



Dec. 5, 1961 H. F. HICKS, JR 3,012,212

BOLOMETER CONSTRUCTION Filed Aug. 25, 1955 HarryE'Hip-ks, J1:

IN VEN TOR.

BY i-n ld/ lw United States Patent 3,012,212 BOLOMETER CONSTRUCTION Harry Frank Hicks, Jr., Rochester, N.Y., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Aug. 23, 1955, Ser. No. 530,218 2 Claims. (Cl.338-18) This invention relates to an improved bolometer construction, and is particularly pertinent to bolometers of the thermally variable resistance type.

One form of bolometer in general use for detecting temperature changes comprises one or more resistance elements, the resistance of which varies in response to changes in radiant heat impinging thereon and which are supported in a suitable glass envelope. While bolometers of this construction are fairly satisfactory, they are open to certain objections. For example the type of construction, which is not unlike that of radio tubes, involves many relatively painstaking operations in the manufacture of the bolometer, as well as a relatively large number of different parts. Moreover, unless such a bolometer is highly evacuated, the gases within the envelope tend to be put in motion, both due to thermal convection currents and also due to mechanical vibrations imparted to the unit as a whole, with the result that there is a tendency for electrical noise, commonly referred to as swish, to be generated in its output. Such stray noise tends to mask the signals which would be otherwise generated by relatively small changes in temperature.

It is an object of this invention to provide a bolometer construction which is relatively simple, consists of but a few parts, many of which are substantial duplicates of one another, and with which there is no necessity of evacuation.

A further object is to provide a bolometer construction in which thermally sensitive elements are rigidly supported between a pair of disk or plate-like members in intimate contact with one another so that there is no appreciable amount of air or other gases present in the immediate vicinity of the thermally-sensitive elements.

Other objects will become apparent from the following description, particularly when taken in the light of the accompanying drawing and appended claims.

In the drawing:

FIG. 1 is a front view of my improved bolometer;

FIG. 2 is a side view thereof;

FIG. 3 is a fragmentary sectional view taken in the plane indicated by the line 3-3 in FIG. 1; and

FIG. 4 is a perspective view showing the parts at an intermediate stage of assembly.

While my invention may be embodied in bolometers of various sizes and shapes, the drawings show one form to which my improved construction is particularly well adapted. As shown in FIGS. 1 and 2, the bolometer comprises a pair of plates or members 1 and 2, which may be in the form of disks arranged to fit closely against one another, and which are provided respectively with grooves 3 and 4 in their contacting faces. The front plate or member 1 is made of a material which is transparent to infrared energy, such, for example, as certain glasses, quartz, polyethylene, or similar materials. The rear plate or member 2 may be of similar material, if desired, or almost any other material which is electrically non-conducting may be employed.

In the groove 3 on the rear surface of front plate 1, a thin, elongated strip or flake 5 of thermally-responsive resistance material is secured as by means of a suitable adhesive 7. A similar flake 6 is likewise adhesively secured in the groove 4 on the front surface of the rear plate member 2. Any of the well-known materials 3,012,212 Patented Dec. 5, 1961 which are commonly used in thermistors may be employed for the flakes 5 and 6.

Any desired number or arrangement of thermally sensitive elements, such as flakes 5 and 6, may be used, depending upon the particular application for which the bolometer is intended. In the present case, it is desired that the flakes 5 and 6 be arranged as a cross and be electrically insulated from one another, and to this end,

a thin piece of dielectric material 8, such as mica, is sandwiched between the two flakes 5 and 6 in the area of intersection, as is best shown in FIGS. 3 and 4. Electrical connections to the ends of flakes 5 and 6 may be made by means of fine platinum wires suitably secured to the ends of the flakes, for example, by means of a platinum-containing electrically conductive adhesive.

Where, as in the present case, it is desired that the flakes 5 and 6 be precisely oriented at a predetermined angle to one another, the plates 1 and 2 may be provided with suitable guide pins 10 and 12 respectively which mate with corresponding holes 11 and 13 in the opposite member to accurately position the plates during assembly. The plates 1 and 2 may be adhesively secured together or, if desired, may be held in firm contact with one another as by means of suitable clamping means (not shown).

In order to show the type of construction, it has been necessary, in the drawing, to exaggerate to a rather considerable degree the thickness of the flakes 5 and 6 and of the spacer 8. In practice flakes 5 and 6 will ordinarily have a thickness of from .0002 to .0005 while the dielectric spacer 8 may have a thickness of from .0002" to .001. As is indicated in F163 the thickness of the adhesive 7 used to retain the flakes in the grooves will normally be considerably greater than the thickness of the flakes themselves. As is also best shown in FIG. 3 the outer surface of each flake is preferably substantially flush with the corresponding surface of the plate or member in which it is mounted so that when the parts are assembled together there will be substantially no air space adjacent the flakes. In order to increase the sensitivity of such a bolometer, it is desirable that the forward surfaces or faces 14, 15 of flakes 5 and 6 be painted with a suitable black, heat-absorbing, nonconductive paint 16. Obviously, the adhesive 7 used to secure the flake 5 in the front member 1 must, like the remainder of plate 1, be transparent to infrared energy.

As can be readily observed from the drawing a holometer of my improved construction involves but relatively few, easily-manufactured parts. Plates l and 2 may be substantially identical and may be formed by the same work operations, the chief difference being in the location of the locating pins 10 and 12. The sensitive flakes 5 and 6 are firmly supported throughout their length so that, in use, they will not be adversely affected by vibration and, since they are each in substantially intimate contact with the opposing face of the adjacent member 1 or 2, there is substantially no chance for any air movement to occur in the vicinity of the flakes such as might cause the unwanted electrical noise previously mentioned.

While my invention has been described with respect to a bolometer responsive to infrared energy, it is believed obvious that the same general type of construction is equally well-adapted for use for detecting radiant flake being substantially flush with said rear surface of said member, and a rigid backing member of electricallynon-conductive material secured/t0 said body in inti-.

mate contact with said rear surface of said front mernher and covering said groove andfthe flake therein, said backing member being provided with an elongated nar row groove in its forward surface, and a second flake of thermally-sensitive resistance material being sec'nr'e'd' and entirely positioned within said lastmentioned groove.

2. A bolometer as set forth in clairnl wherein said second groove extends transversely of said first groove and wherein a spacer of dielectric material is interposed between said flakes in the area of intersection of said grooves.

References Cited in the file of this patent UNITED STATES PATENTS 1,904,139 Henkel Apr. 18, 1933 2,036,457 Calsow Apr. 7, 1936 2,039,083 Keiffer Apr. 28, 1936 2,114,591 Clark Apr. 19, 1938 2,183,256 'Gabler Dec. 12, 1939 Hewlett Apr. 9, 

